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The Mn-Zn ferrite nanoparticles with a spinel structure were successfully prepared by using chemical co-precipitation method. The formed magnetic ferrite particles were coated on the surface of Fe-6.5 wt%Si alloy particles with the epoxy resin to prepare the powder core. The influence of magnetic ferrite insulation on the magnetic properties of the powder core was studied. Insulating with a moderate quantity of ferrite was found to improve the effective permeability and the loss of the powder core, while the inadequate insulation and the excessive insulation with ferrite led to the rapid growth of the eddy-current loss at high frequency and the remarkable decrease of the effective permeability, respectively. The effective demagnetizing field determined by the core’s density and the magnetic nature of the ferrite were proposed to be the main causes of the variation of the core’s magnetic performance. Loss separation fitting revealed that the hysteresis loss is much higher than the eddy-current loss for the core measured at the frequency lower than 120 kHz. This suggested that improving the effective permeability and the loss of the powder core in low-frequency range should focus on the means of reducing the effective demagnetizing field.

Fe–Si–Cr–B amorphous and carbonyl-iron powders insulated with phosphoric acid solution were used to prepare soft magnetic composites. The mass ratios of phosphoric acid insulation solution and the carbonyl-iron powder dependences of the magnetic spectrum, the density, and the resistivity were studied. Both the real part and the imaginary part of the core’s complex permeability increased after an initial decrease with the acid mass ratio increasing. This is similar to the variation tendency of the core’s density and opposite to the variation tendency of the core’s resistivity. The amount of the air gap, reflected by the density, was proposed to be the most important factor that has a great influence on the composite’s magnetic properties. The increase of the air gap reduced the effective demagnetizing field and the resistivity. This improved the permeability and the hysteresis loss and deteriorated the eddy-current loss. Carbonyl-iron powder addition was found to improve the moldability and the permeability of the composite based on the Fe-Si-Cr-B amorphous powder, although its loss was higher than that of the amorphous powder. All these findings can be referenced when designing an amorphous-based soft magnetic composite (SMC) core with balanced permeability, loss, and cost for high-frequency inductor within a MHz band.

In this experiment, the microstructure and toughness of the heat-affected zone of samples under different t8/5 times were monitored. According to the results, 100% bainite transformation took place in the heat-affected zone under a rapid cooling rate. The bainite content decreased, and the ferrite content increased with prolonged t8/5. The impact toughness of the heat-affected area was shown to vary with its microstructure. The tests demonstrated that the normalised zone showed good weldability with a fine microstructure, and the impact toughness was optimised when t8/5 of the over-heated and partial transition zones was between 10 and 15 seconds. Cooling cracks could be prevented by preheating at a temperature of 50°C, and was shown using the oblique Y test. This study supports the high weldability of SA738Gr.B steel.

In this paper, thermoelectric materials of pure Mg2Si, Mg2Si1-xSnx and 1% Bi-doped Mg2Si were prepared by a low-temperature solid-state reaction using MgH2, Sn and Si, followed by a field-activated and pressure-assisted sintering process for consolidation. The reaction between silicon, tin and magnesium hydride, instead of pure magnesium, minimises the oxidation and volatilisation of magnesium. After consolidation, the prepared thermoelectric materials, which had a grain size of 500 nm, were evaluated for their thermoelectric properties. Furthermore, the electrical and thermal conductivities and the Seebeck coefficient were measured over the temperature range of 300–750 K. A sample of 1% Bi-doped Mg2Si showed a maximum figure of merit, ZT, of 0·53 at 750 K. Additionally, the Mg2Si1-xSnx samples were seen to possess an extra low thermal conductivity. The results are discussed in comparison with previously reported values and a prediction of modelling studies.

Microscopic experiments were performed on the inner pores of calcareous sand particles to ascertain the special mechanical properties of calcareous sand. A femtosecond laser was used to cut the calcareous sand particles to obtain cross-sections of particle. The micrographs of the inner pores of the sand particles were taken with a three-dimensional video microscopic visualiser. The parameters of the pores were analysed through the micrograph processing with MATLAB. The results show that calcareous sand has relatively low surface porosity. The surface porosities of particles with pore diameter >2 mm and those in the range of 1–2 mm are 0·66 and 1·07% respectively. Based upon the number of pores, the distribution characteristics of the pores show that there are fewer macropores but more micropores in the sand. In terms of the area of pores, micropores occupy a smaller proportion than macropores. It was found that 65% of the pores have area

Weld joints of S32101 duplex stainless steels are aged at 700°C for different periods of time after solution treatment at 1050°C. The microstructures of the weld and heat affected zone (HAZ) were examined by optical microscopy, scanning electron microscopy and transmission electron microscopy, and low temperature impact test and potentiodynamic polarisation corrosion test were performed on the weld joints. Results show that solution treatment at 1050°C improves microstructure and properties. Precipitation phase of Cr2N is precipitated in the weld and HAZ after aging treatment at 700°C and with increase in aging time precipitation phase of Cr2N grows, which results in the reduction in impact toughness and transition of fracture features from ductile dimples to brittle cleavages. Pitting corrosion occurs inside the ferrites of solution treated samples, and pitting corrosion occurs in secondary austenite around the precipitation phases of Cr2N for aging treated samples, and with the increase in aging time, t...

An all-fiber, wavelength-tunable, passively mode-locked erbium-doped ring laser is presented. Erbium-doped fibers (EDF) are used as the gain media because of their large gain bandwidth. Nonlinear polarization rotation (NPR) plays the dual role of realizing mode-locking and effectively adjusting the intensity-dependent loss of the cavity. An unbalanced Mach-Zehnder interferometer (UMZI) is used as a tunable optical beam filter. By using the UMZI and adjusting the polarization controllers (PCs), a sub-picosecond mode-locking laser is realized that is self-starting with central lasing wavelengths that can be accurately tuned over a range of about $\sim $ 30 nm and also has controllable spacings between different tunable wavelengths.

The Menard pressuremeter test can be successfully performed at any depth, this pressuremeter (designated by PMT) has a greatest advantage for seabed and other underwater tests from floating platforms, since there is no need for a stiff linkage between the probe and the drilling platform. In-situ test of a bridge foundation ground, envolving underwater sedimentar soft clay and sand by using GA pressuremeter, is introduced. Based on the interpretation of drill borehole geologic data, a linear relationship between standard penetration test values (N 63.5 ) and bearing capacity of foundation based on pressuremeter test was assumed. The correlation between N 63.5 and bearing capacity of foundation derived from PMT are different because of the difference of soil properties. For hard soil foundation, the increasing degree of bearing capacity of foundation calculated from pressuremeter test with N 63.5 is small. And the increasing degree of bearing capacity of foundation calculated from pressuremeter test with N 63.5 is rather large for soft soil foundation. It can be well used for ascertaining the ground bearing capacity by SPT and partial pressuremeter test data and determining the position of supporting course.

We describe a reliable fabrication procedure of silver tips for scanning tunneling microscope (STM) induced luminescence experiments. The tip was first etched electrochemically to yield a sharp cone shape using selected electrolyte solutions and then sputter cleaned in ultrahigh vacuum to remove surface oxidation. The tip status, in particular the tip induced plasmon mode and its emission intensity, can be further tuned through field emission and voltage pulse. The quality of silver tips thus fabricated not only offers atomically resolved STM imaging, but more importantly, also allows us to perform challenging "color" photon mapping with emission spectra taken at each pixel simultaneously during the STM scan under relatively small tunnel currents and relatively short exposure time.